1. Field of the Invention
This invention relates to a multifunction apparatus having a copier function and a printer function, and more particularly to an image formation apparatus in which said two functions are performed at a time to synthesize an original image and an electrical signal image.
2. Description of the Prior Art
At present, multifunction apparatus having both the function of a copier producing copies from originals and the function of a printer utilizing such copier function to produce copies from an input (electricity, magnetism or the like) other than originals are about to be put into practical use.
As a system in which such copier function and other image recording function are combined together to obtain a combined image consisting of the exposure images by the respective functions, there has been known and proposed an overlay system utilizing the electrophotographic system. For example, systems in which the conventional xerography system is utilized to expose a photosensitive plate to an original of a form to be overlaid in the xerographic process and then data written into this form is imparted to the photosensitive member are disclosed in U.S. Pat. Nos. 3,045,587 and 3,523,725.
Also, systems which, unlike the above-mentioned systems, utilize the NP electrographic process as disclosed in U.S. Pat. Nos. 3,666,363 and 4,071,361 to obtain an overlay image are described in U.S. Pat. No. 4,122,462 and U.S. applications Ser. Nos. 935,987 now U.S. Pat. No. 4,257,701; 104,704 now abandoned and 121,657 now U.S. Pat. No. 4,329,413 of the assignee of the present invention.
In these overlay systems, a moving photosensitive member is sequentially exposed to a first image and a second image or optical image to be overlaid and therefore, the positioning for overlaying the two images on the photosensitive member is desired during the respective times of exposure or recording.
The above-described overlay technique is a method of complex utilization of the copier function and another image information recording function. There have heretofore been needs for a system having such multiple functions, but concrete proposals for realizing one have been limited.
As regards the needs, a multifunction apparatus having both the copier function and the printer function has merit in that the apparatus itself can be made compact and low in cost because some of the components of a single function copier and printer can be made common to one another. Further, in such an apparatus, not only the working ratio of the apparatus can be increased by selectively using the copier function and the printer function, but also the respective functions can be performed at a time to obtain a hard copy in which an original image and an electrical signal image are combined together. According to this, photographs requiring half tone or pictures, graphs, forms or the like which are difficult to encode can be copied with the copier function while, at the same time, writings edited by a word processor can be copied with the printer function.
Generally, in the conventional image recording apparatus such as electrophotographic copying machines, the photosensitive member used is of a larger size than the size of the originals to be copied. This is to enable the apparatus as an office copier to select a plurality of original sizes (for examples, JIS A3, A4, B4, B5 formats). Also, even in apparatus wherein the size change-over is not effected, the charging width for the photosensitive member is usually greater than the image exposure width in order to eliminate an unsatisfactory charging effect, and with the transfer type apparatus, it is usually the case that for convenience of a device for separating transfer paper from the photosensitive member, the end area of the photosensitive member in opposed relationship to which such separating member is disposed is left as the non-imaged area. For these reasons, it is unavoidable that the non-imaged area is formed on the photosensitive member. If the step shifts to the visualizing process when charge or potential remains in this non-imaged area, developer such as toner would adhere to the non-imaged area, which means wasteful consumption of the developer, and moreover, the developer adhering to such non-imaged area would not be transferred to transfer paper but would remain on the photosensitive member, so that with rotation of the photosensitive member, such developer would adhere or scatter to the developing station, the cleaning station and other process stations to contaminate these stations excessively.
To solve such problem, there is a method of stopping the rotation of the developing device in the non-imaged area of the photosensitive member to thereby suppress the developing effect, or in cases where a rotatable magnet brush is used in the developing device, a method of using a plate member in the non-imaged area of the photosensitive member to reduce the brush height of the magnet brush and thereby suppress the developing effect.
However, the above-described mechanical means for solution repetitively requires the rotating apparatus to be suddenly stopped, started and moved and this prevents higher speed of the image recording apparatus.
As a solution to this problem, a method of irradiating the non-imaged area of the photosensitive member by an auxiliary exposure device (hereinafter referred to as the blank exposure) to thereby cause the surface potential of the non-imaged area to disappear is effective. From the convenience with which such blank exposure can be freely imparted, a copier-printer apparatus having the previously described printer function is the more effective as well.